1. Field of the Invention
The present invention relates to a rotary connector device which establishes an electrical connection between a vehicular body and a steering wheel in an automobile.
2. Description of the Related Art
In some of vehicular rotary connector devices, an annular space is formed between a rotor connected to a steering shaft and a stator fixed to a vehicular body side and a flat cable is arranged in the annular space for establishing a connection between the side of the rotor and the side of the stator.
FIG. 6A and FIG. 6B are diagrams each schematically explaining an arrangement of a flat cable 101 provided in an annular space S in a conventional rotary connector device 100, wherein FIG. 6A is a diagram showing a state where a spacer 104, which is incorporated in a position (neutral position) where the flat cable 101 can perform two rotations in the right and left directions, is normally incorporated in the rotary connector device 100, and FIG. 6B is a diagram showing a state where the spacer 104 is incorporated in a position (non-neutral position) where the flat cable 101 can not perform two rotations equally in the right and left directions, and a length of the flat cable 101 comes short in the middle of operating an unillustrated steering wheel.
As shown in FIG. 6A, the flat cable 101 goes through between ribs 104a and 104a and is pulled out from an inner diameter side to an outer diameter side of the spacer 104 in the annular space S. The flat cable 101 positioned in the inner diameter side of the spacer 104 is wound in one direction around an outer periphery of a rotor 102, and thereafter is connected to a connector 102a at the side of the rotor. In addition, the flat cable 101 positioned in the outer diameter side of the spacer 104 is wound around the outer periphery of the rotor 102 in the opposite direction to the inner diameter side, and thereafter is pulled out from an opening 105 of an annular wall 103 to an outside of the annular space S, and finally is connected to a connector (not shown) at the side of the stator.
The flat cable 101 is adapted to move between the inner diameter side and the outer diameter side of the spacer 104 in association with an operation of the steering wheel, and a rotatable angle range of the steering wheel is to be defined in accordance with a length of the flat cable 101. The length of the flat cable 101 is set such that the steering wheel can performs at least two rotations in the right and left directions from the neutral position. Therefore at the time of mounting the rotary connector device 100 on a vehicle, the rotary connector device 100 is designed to be incorporated in a steering shaft in a state where the spacer 104 is set in a position (neutral position) such that the flat cable 101 can perform two rotations in the right and left directions. At this time, the rotor is temporarily fixed to the stator by a retainer to prevent the neutral position of the flat cable from deviating (to restrict rotation of the rotor).
Herein, as the problem that the retainer unfastens and the rotor rotates occurs at the incorporating, the rotary connector device 100 possibly results in being incorporated in the steering shaft in a state where the flat cable deviates from the neutral position. In this case, the length of the flat cable comes short in the middle of rotating the steering wheel depending on the deviation amount from the neutral position, thus creating a possibility of interrupting the operation of the steering wheel.
In a case where this event occurs, the flat cable 101 is pulled in association with the operation of the steering wheel to be strongly pressed against the opening 105 of the annular wall 103 (refer to FIG. 6B). Therefore the conventional rotary connector device is configured such that, a cutter is provided in the opening 105, and in a case of occurrence of this event, the flat cable 101 is cut by the cutter, thus preventing the operation of the steering wheel from being interrupted (for example, refer to Japanese Patent Laid-Open Publication No. 2001-28286).
FIG. 7A is an exploded perspective view of a stator 110 in a rotary connector device disclosed in Japanese Patent Laid-Open Publication No. 2001-28286, and FIG. 7B is an enlarged diagram showing part of a projection 115 (cutter) provided in a cover 112 of the stator 110 in the rotary connector device.
The stator 110 is provided with a bottom cover 111 mounted and fixed to the vehicular body side and the cover 112 incorporated in the bottom cover 111, and an annular wall 113 is provided in the cover 112 for surrounding an outer periphery of a rotor (not shown) by a predetermined interval. As the cover 112 is incorporated in the bottom cover 111, an annular space S surrounding the outer periphery of the rotor (not shown) is formed inside of the annular wall 113, and a spacer 104A formed in a ring shape as viewed in an axial direction is rotatably accommodated in the annular space S. In addition, the flat cable 101 for connecting the side of the rotor and the side of the stator is provided in a state of being wound around the spacer 104A.
An opening 114 is provided in the annular wall 113 for drawing one end 101a of the flat cable 101 to an outside of the annular space, and the projection 115 (cutter) is provided in one side 113a of the opening 114 in the circumferential direction for cutting the flat cable 101. The projection 115 is provided to project from one side 113a of the opening 114 toward the other side 113b, and is formed in a substantially rectangular shape as viewed in a radial direction.
Here, in a case where a length of the flat cable 101 comes short in the middle of rotating the steering wheel due to the event that the flat cable 101 is wound around the spacer 104A in a state of deviating largely from the neutral position, the flat cable 101 results in being pulled in a direction (left direction in the figure) of making contact with the projection 115. In addition, after a corner portion 115a of the projection 115 makes contact with the flat cable 101, as the flat cable 101 is further pulled, stress concentrates on apart of the flat cable 101 making contact with the corner portion 115a of the projection 115, so that the flat cable 101 is cut centering around the part on which this stress concentrates.
However, for preventing the corner portion 115a of the projection 115 from damaging the flat cable 101 in a case where such an event does not occur, the corner portion 115a is formed in a circular shape. Therefore in a case where the flat cable 101 makes contact with the corner portion 115a, there occurs a problem that the retaining of the flat cable 101 can not be certainly performed. Therefore in a case where the flat cable 101 is pulled out toward the projection 115, in some cases the flat cable 101 deviates toward the part side (upper side in the figure) where the projection 115 is not provided. In this case, the contact position of the corner portion 115a with the flat cable 101 is changed and the stress does not concentrate on a specific part of the flat cable 101. As a result, there are some cases where the flat cable 101 can not be cut.
Therefore, it is required to be able to certainly cut the flat cable 101 when necessary.